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    Petrified Forest

    National Park Arizona

Petrified Forest Summer of Science 2013

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Date: September 16, 2013
Contact: Brad Traver, 928-524-6228 x245

Petrified Forest—There is always science going on at Petrified Forest National Park—September is the time for a summary of the summer's activity. Every year, seasonal employees, researchers, and summer interns swell the park's science staff and get out into the field to make new discoveries.

Paleontology

The paleontology work was focused in two areas. The first was recovering fossils from a known fossil-producing locality on lands recently acquired by The Conservation Fund on the park's behalf. The lands are in the expansion area of the park, were owned until this year by the McCauley family partnership, and are being purchased from The Conservation Fund by the National Park Service. The Conservation Fund provided permission for the excavation. The second area of focus was beginning a "histology" project. Histology is the study of the cellular structure of fossilized animal bone that has been sliced so thin that light passes through it.

The fossil-producing site was known because there have been bones eroding from its surface for years. If they are allowed to weather, they are lost to science so excavating into the site to retrieve un-weathered fossil bone is important in the highly erodible soils of the area. Several fossils were found—the skull of a phytosaur was first. Phytosaurs are the distant ancestors of modern crocodiles and were common in the river systems that existed here 220 million years ago. The skulls, however, almost always detach from the rest of the skeleton and can be harder to locate. The specimen skull found is approximately 2 feet long and is very well preserved, especially the palate. The second find from the site is Doswellia, a close-relative of the phytosaurs, and a new find for Petrified Forest National Park. Scientists have known that these animals should exist in the ecosystem and time period represented at the park but had never found one, until this summer. The particular species of Doswellia found, D. kaltenbachi, is the first record of this species found in the western United States. And, lastly, some particularly good aetosaur neck plates from the species Desmatosuchus spurensis were found and immediately used in a public display at the Rainbow Forest Museum. Desmatosuchus bones are very rare in the park.

Beyond the fossil bones, a new rich layer of fossil material was identified a few inches lower (and thus older) than the layer bearing the bones mentioned above. Further research will await an opportunity to get back to that site. And the site is important for another reason—the layer bearing the fossils that have been excavated so far seems to be the bottom of an ancient pond and has turned up numerous bones of fish, amphibians, and reptiles. Continuing to excavate that layer has the potential to eventually describe the ecosystem of that pond—what animals were living there and, if plant fossils are found, what was growing there. In addition to the large animals, fossils of small creatures are also found in these excavations and add to the story. These are especially important as smaller animals are only preserved under special circumstances and are generally unknown in the fossil record.

Getting started on histology this summer is an exciting new field at the park because it has the potential to provide much more depth to the story of the ancient landscape. By looking at the cellular structure of the fossil bones, scientists can tell the age of the animal, how fast it grew, and possibly whether it was male or female. Having this knowledge can help better define the ecosystems in which they lived. For example, a productive fossil site in the Painted Desert provides bones of diverse groups such as amphibians, crocodile ancestors and early dinosaurs. Scientists have examined the histology of these types of animals in the past, but from different localities that represent different times and environments. Here we can examine all of these different animal groups from the same time and environment and see if these factors affected growth rates and styles for these different animal groups. Park scientists don't know of any other fossil site in the world with this much potential for detailed definition. In another example, in the Revueltosaurus quarry excavated last year, where 11 individuals of the same species have been found in close proximity (unique in the world), examining the cellular structure of the same bone from each animal will give scientists ages and potentially genders for individuals which may help explain why they were all living together in the same place at the same time.

Paleontologist and paleontology program contact: Mr. William Parker 928-524-6228 x 262 Summer Interns: Sarah Tulga, Adam Marsh, Zachary Morris, and Kelsey Hornung.

 

Archeology

The park's archeological program had a shot in the arm this year, successfully competing for project funds to begin a systematic identification and recording of archeological sites on the ranch lands acquired in 2011 within the expanded boundary of Petrified Forest. Starting with areas close to roads, two crews explored their assigned areas and made important discoveries.

The red team explored about 160 acres (of the 26,000 acres purchased in 2011) and found and recorded about a fifteen archeological sites, ranging from small one-room field houses to slightly larger multi-room pueblos from the Pueblo II and Pueblo III period (800-1000 years ago). This density of sites was higher than expected and, should it be representative of the area as a whole, would reveal an exceptionally dense use of the area. One of the field houses held a cache of 7 stone axe heads, which is highly unusual. Since each axe head represents a great deal of effort, a collection of them is a rare find. We suspect the raw material for the heads came from New Mexico and working of the stone took many hours of grinding and polishing. A wide variety of pottery types were represented in the sherds found at these sites. Park archeologists are exploring whether all the pottery came from other areas of the region or whether some may have been locally made and decorated to mimic designs from elsewhere. Thin sectioning the sherds (cutting very thin slices that can be examined under a microscope) helps scientists identify the materials used in pottery manufacture; when then matched with local material availability, may help answer this question.

The gold team only needed a few minutes at their assigned survey area to identify a large Basketmaker site from about 1300 years ago. Features of the site include pit houses, storage cists, and flaking stations (for the making of stone tools and weapons). This Basketmaker site also has later occupations represented by Puebloan field houses. Incredibly, this team found a second, even larger Basketmaker site nearby that had evidence of Archaic (much earlier) occupation, too. Together, just these two sites represent occupation of the area from about 5000BCE to about 1350CE – a span of over 6000 years! At the second Basketmaker site, archeologists recorded 42 features including living quarters, storage areas, flaking stations, and even a water control feature. Most exciting was a site used to manufacture shell ornaments. Shell blanks, finished ornaments, and specialized tools were all found at the site. All together, the gold team found these two Basketmaker sites, and another ten sites on about 90 acres – more unexpected high density occupation. The Basketmaker sites are particularly important due to their large size, the relative scarcity of undisturbed sites in our region, and most importantly, the landscape (grassland dune ridge) they are found in. The park currently has sites on high mesas or on ridge crests but not (until now) on the lower landscape positions like these dune ridges. These could be important additions to our knowledge of the Basketmaker period in our area.

After being chased out of the lowlands by monsoon season, crews began recording another pit house village from the early Pueblo period of a more modest size—about 20 rooms. Their season ended before that record was complete, although work will continue in the fall. They also mapped two Pueblo II period sites of 12-20 rooms with some interesting features like raised platforms which may indicate affiliation with Chacoan culture.

Lead Archeologist and archeology program contact: Mr. William Reitze 928-524-6228 x 268. Archeologist: Iva Lee Lemkuhl. Seasonal archeologists: Gregory Luna Golya, Erina Gruner, Robert Sinesky, Kathleen McConnell. Summer Interns: Crystal Simms, Emmy Kvamme, Stephanie Mack, Samantha Linford.

 

Park scientists continue field work on a smaller scale through the fall, winter, and spring while preparing for another busy summer in 2014. They expect to make more new and important discoveries then.

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